JP2021071107A - Centrifugal blower - Google Patents

Abstract

To provide a centrifugal blower which can further reduce noise without lowering a wind volume characteristic of a fan by further optimizing a range of a ratio of inside diameters and outside diameters of blades of the centrifugal blower.SOLUTION: A centrifugal blower accommodates an impeller in a casing which is constituted of an upper casing and a lower casing, and blows out air to the outside of the casing from an opening which is formed at a side face of the casing. The impeller comprises a circular plate-shaped shroud in which an opening is formed at its center, a circular plate-shaped main plate, and a plurality of blades arranged between the shroud and the main plate. When setting a diameter of a virtual circle passing an internal peripheral edge of the blade as d, and setting a diameter of an external peripheral edge of the shroud as D, a ratio d/D of the diameter d with respect to the diameter D is lower than a value in which a natural frequency of the impeller with respect to the ratio d/D becomes the lowest.SELECTED DRAWING: Figure 2

Description

The present invention relates to a centrifugal blower.

Centrifugal blowers are known as blowers widely used for cooling, ventilation, and air conditioning of home appliances, OA equipment, and industrial equipment, as well as for vehicle air conditioning and ventilation.

As a conventional centrifugal blower, a centrifugal fan having a configuration in which air is blown out of the casing from an opening formed on a side surface of a casing composed of an upper casing and a lower casing over the entire circumference is known (for example, Patent Documents). See 1).

For such a centrifugal blower, there is a demand for improvement of air volume characteristics and noise reduction. In response to such a demand, it seems effective to increase the chord length of the blade to reduce the load on the blade and improve the rigidity of the impeller. It is considered that by increasing the chord length of the blade, the load per unit length of the blade is reduced, and the force acting on each part of the blade that causes vibration can be weakened. Further, it is considered that by increasing the chord length of the blade, the impeller is reinforced over a wide range by the blade, and the rigidity can be increased.

Further, for the blade, the fan efficiency can be increased by setting the ratio (D1 / D2) of the innermost inner diameter (D1) to the outermost outer diameter (D2) to 0.5 or less. , A blower fan capable of achieving low noise has been proposed (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2012-189047 Japanese Unexamined Patent Publication No. 2005-240798

However, in the blower fan shown in Patent Document 2, the fan efficiency can be increased and the noise can be reduced by setting the inner / outer diameter ratio (D1 / D2) of the blades to 0.5 or less as described above. However, it is said that there is not much effect when the inner-outer diameter ratio is 0.4 or less.

On the other hand, in the conventional centrifugal blower as described in Patent Document 1, the inner / outer diameter ratio of the blades is generally set in the range of 0.4 to 0.5, which is the range specified in Patent Document 2. There is no big difference.

As described above, the centrifugal blower has been devised to reduce the noise, but depending on the application in which the centrifugal blower is used, it is required to further reduce the noise.

The present invention has been made in view of the above, and by further optimizing the range of the inner / outer diameter ratios of the blades of the centrifugal blower, it is possible to further reduce the noise without deteriorating the air volume characteristics of the fan. It is an object of the present invention to provide a centrifugal blower capable of producing.

In order to solve the above-mentioned problems and achieve the object, the centrifugal blower according to one aspect of the present invention accommodates an impeller inside a casing composed of an upper casing and a lower casing, and is formed on the side surface of the casing. It is a centrifugal blower that blows air out of the casing through the opening. The impeller includes a disc-shaped shroud having an opening at the center, a disc-shaped main plate, and a plurality of blades provided between the shroud and the main plate. When the diameter of the virtual circle passing through the inner peripheral edge of the blade is d and the diameter of the outer peripheral edge of the shroud is D, the ratio d / D of the diameter d to the diameter D is the impeller with respect to the ratio d / D. The natural frequency of is less than the lowest value.

The centrifugal blower according to one aspect of the present invention can further reduce noise without deteriorating the air volume characteristics of the fan by further optimizing the range of the inner / outer diameter ratio of the blades of the centrifugal blower.

FIG. 1 is an external perspective view of the centrifugal blower according to the embodiment. FIG. 2 is a vertical sectional view of the centrifugal blower (AA sectional view in FIG. 1). FIG. 3A is an example (1) of a view of the impeller viewed from the axial direction. FIG. 3B is an example (2) of a view of the impeller viewed from the axial direction. FIG. 3C is an example (3) of a view of the impeller viewed from the axial direction. FIG. 4 is a graph showing an example of a change in the natural frequency of the impeller with respect to the inner / outer diameter ratio (d / D) of the blade. FIG. 5 is a graph showing an example of a change in the power consumption of the centrifugal blower with respect to the inner / outer diameter ratio (d / D) of the blades.

Hereinafter, the centrifugal blower according to the embodiment will be described with reference to the drawings. The present invention is not limited to this embodiment. In addition, the relationship between the dimensions of each element in the drawing, the ratio of each element, and the like may differ from reality. Even between drawings, there may be parts where the relationship and ratio of dimensions are different from each other. Further, in principle, the contents described in one embodiment or modification are similarly applied to other embodiments or modifications.

FIG. 1 is an external perspective view of the centrifugal blower 1 according to the embodiment. Further, FIG. 2 is a vertical sectional view of the centrifugal blower 1 (AA sectional view in FIG. 1).

In FIGS. 1 and 2, the centrifugal blower 1 is composed of a lower casing 2 and an upper casing 3. The structure is such that air is blown out of the casing from the air outlet 6 which is an opening formed on the side surface of the casing over the entire circumference. An impeller 7 and a motor 8 for rotating the impeller 7 are housed in the casing.

An opening 3d serving as a suction port 5 is formed in the center of the upper casing 3, and a plurality of columns 4 are interposed between the lower casing 2 and the upper casing 3 to connect the lower casing 2 and the upper casing 3. ing. The connection between the support column 4 and the lower casing 2 may be, for example, a fastening material (screw), or may be one in which the tip end portion of the support column 4 is projected to the back side of the lower casing 2 and then the tip end portion is heat-caulked. On the side surface of the casing, the openings formed between the columns 4 form the air outlet 6.

The upper casing 3 is made of, for example, resin. The upper casing 3 has an opening 3d serving as a suction port 5 in the center, and two steps 3b and 3c are formed on the peripheral edge of the suction port 5. A plurality of ribs 3f are formed radially and concentrically on the surface of the flat portion 3a on the outer peripheral side of the outer step portion 3b, and the recess 3g is adjacent to the rib 3f (FIG. 2).

On the lower surface of the upper casing 3, an annular recess 3e is formed on the peripheral edge of the opening 3d serving as the suction port 5, and an annular protrusion formed on the peripheral edge of the opening of the shroud 7d of the impeller 7 in the annular recess 3e. A part of 7e is housed and functions as a labyrinth seal. Further, a recess (step) 3h is formed on the lower surface of the upper casing 3, and the upper surface of the shroud 7d of the impeller 7 is accommodated in the recess 3h. The upper casing 3 and the plurality of columns 4 are formed, for example, by integrally molding a resin.

The impeller 7 includes a disc-shaped main plate 7a, a disc-shaped shroud 7d having an opening in the center, and a plurality of (for example, 13) blades 7c provided between the shroud 7d and the main plate 7a. It has. The blades 7c, for example, all have the same shape, are arranged at equal intervals in the circumferential direction, and are curved convexly with respect to the rotation direction of the impeller 7.

Since the opening of the shroud 7d is located at a position facing the opening 3d (suction port 5) of the upper casing 3, the air sucked from the opening 3d of the upper casing 3 is guided between the blades 7c through the opening of the shroud 7d. The air guided between the blades 7c is blown out from the outer peripheral edge of the impeller 7 and blown out of the casing through the opening (outlet 6) on the side surface of the casing.

The lower casing 2 is made of metal, for example. The motor 8 is attached to the lower casing 2. The motor 8 is, for example, an outer rotor type three-phase brushless DC motor. For example, a metal bearing holder 10 having a pair of bearings 11 mounted inside is caulked and fixed to the opening 2a formed in the center of the lower casing 2. The lower casing 2 may be made of resin, and in that case, the bearing holder 10 may be press-fitted or insert-molded.

The shaft 9 is rotatably supported by a pair of bearings 11 mounted inside the bearing holder 10. The shaft 9 is made of metal, for example, and one end of the shaft 9 is coupled (press-fitted) to a boss-shaped hub 7b formed in the center of the main plate 7a of the impeller 7. The impeller 7 and the shaft 9 may be integrally formed by insert molding.

A stator core 12 having a plurality of teeth extending outward in diameter from the annular core back portion was mounted on the outer peripheral surface of the bearing holder 10, and both sides of the stator core 12 in the axial direction were formed of, for example, an insulating resin. An insulator 13 is provided, and a coil 14 is wound around each tooth via the insulator 13. A circuit board 17 is arranged below the insulator 13.

A cylindrical wall 7f is integrally formed on the lower surface of the disk-shaped main plate 7a of the impeller 7. An annular back yoke 15 made of a soft magnetic material is fixed to the inner peripheral surface of the cylindrical wall 7f, and an annular magnet 16 is fixed to the inner peripheral surface of the back yoke 15. The magnet 16 is arranged to face the teeth of the stator core 12. The shroud 7d, the main plate 7a, the plurality of blades 7c, and the cylindrical wall 7f are formed, for example, by integrally molding a resin.

3A to 3C are examples of views of the impeller 7 viewed from the axial direction, and the hub 7b at the center of the impeller 7 is not shown. In FIGS. 3A to 3C, the diameter of the virtual circle passing through the inner peripheral edge of the blade 7c of the impeller 7 is d, and the diameter of the outer peripheral edge of the shroud 7d (approximately equal to the diameter of the virtual circle passing through the outer peripheral edge of the blade 7c) is D. As a result, the ratio d / D of the diameter d to the diameter D is changed. In FIG. 3A, for example, D = 90 mm, d = 36.25 mm, and the ratio d / D≈0.4. In FIG. 3B, for example, D = 90 mm, d = 27 mm, and the ratio d / D≈0.3. In FIG. 3C, for example, D = 90 mm, d = 18 mm, and the ratio d / D≈0.2.

As is clear from FIGS. 3A to 3C, as the ratio d / D decreases, the blade 7c approaches the center side of the impeller 7, so that the chord length of the blade 7c increases. By increasing the chord length of the blade, it is expected that the load on the blade will be reduced and the rigidity of the impeller will be improved.

Table 1 below shows the results of computer simulation analysis of the natural frequency (Hz) of the impeller 7 with respect to the ratio (d / D) of the diameter d (inner diameter of the blade 7c) to the diameter D (outer diameter of the impeller 7). FIG. 4 is a graph of this. FIG. 4 is a graph showing an example of a change in the natural frequency of the impeller 7 with respect to the inner / outer diameter ratio (d / D) of the blade 7c.

As is clear from FIG. 4, when the ratio (d / D) is about 0.3, the natural frequency is the smallest, and when the ratio (d / D) is smaller than about 0.3, the natural frequency gradually increases. It gets higher. In this region, it is considered that the natural frequency is increased due to the increase in the rigidity of the impeller 7 due to the increase in the chord length of the blade, and the effect of reducing noise can be expected. Therefore, setting the ratio d / D to a state in which the natural frequency of the impeller 7 with respect to the ratio d / D is smaller than the minimum value can be used as one design index.

Further, in FIG. 4, at points P1 to P2 corresponding to the ratio (d / D) = 0.4 to 0.5 in the conventional centrifugal blower, the rigidity of the impeller 7 decreases due to the decrease in the chord length. At the same time, the natural frequency is increased due to the decrease in the mass of the impeller 7. The ratio of point P2 of 0.5 is almost the maximum point in design.

Further, when the ratio (d / D) shown as the region R is about 0.2 or less, it becomes higher than the natural frequency in the ratio (d / D) = 0.4 to 0.5 in the conventional centrifugal blower. By increasing the natural frequency of the impeller 7, the vibration can be reduced, so that the noise of the centrifugal blower 1 can be reduced. Therefore, in order to clearly distinguish it from the conventional one, the ratio (d / D) in the region R can be used as a design index. If the ratio (d / D) is about 0.1 or less, manufacturing difficulty increases, so that the ratio (d / D) is preferably about 0.1 or more.

FIG. 5 is a graph showing an example of a change in the power consumption of the centrifugal blower 1 with respect to the inner / outer diameter ratio (d / D) of the blade 7c. That is, it is the result of measuring the power consumption of the centrifugal blower 1 when the ratio (d / D) is 0.4, 0.3, and 0.2, respectively. When the ratio (d / D) is 0.2, the ratio (d / D) is 0.3, which is almost the same as when the ratio (d / D) is 0.4. From this, when the ratio (d / D) in the impeller 7 is 0.3 or less, it is possible to reduce the vibration and noise without lowering the air volume efficiency (fan efficiency) of the centrifugal blower 1.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

As described above, the centrifugal blower according to the embodiment is a centrifugal blower in which an impeller is housed inside a casing composed of an upper casing and a lower casing, and air is blown out of the casing from an opening formed on a side surface of the casing. The impeller is provided with a disc-shaped shroud having an opening in the center, a disc-shaped main plate, and a plurality of blades provided between the shroud and the main plate, and provides an inner peripheral edge of the blades. When the diameter of the virtual circle passing through is d and the diameter of the outer peripheral edge of the shroud is D, the ratio d / D of the diameter d to the diameter D is larger than the value at which the natural frequency of the impeller with respect to the ratio d / D is the lowest. small. As a result, by further optimizing the range of the inner / outer diameter ratio of the blades of the centrifugal blower, it is possible to further reduce the noise without deteriorating the air volume characteristics of the fan.

Further, the ratio d / D is 0.2 or less. As a result, the natural frequency can be made higher than that of the conventional centrifugal blower, and the noise can be further reduced.

Further, the ratio d / D is 0.1 or more. This makes it possible to eliminate manufacturing difficulties.

Further, the shroud, the main plate, and the blade are integrally formed. Thereby, the impeller can be easily manufactured.

Further, the back yoke and magnet of the outer rotor type motor are fixed to the inner surface of the cylindrical wall provided on the surface of the main plate opposite to the shroud. Thereby, the drive mechanism of the impeller can be easily configured.

Moreover, the present invention is not limited by the above-described embodiment. The present invention also includes a configuration in which the above-mentioned components are appropriately combined. Further, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

1 Centrifugal blower, 2 Lower casing, 3 Upper casing, 4 struts, 5 suction ports, 6 outlets, 7 impellers, 8 motors, 9 shafts, 10 bearing holders, 11 bearings, 12 stator cores, 13 insulators, 14 coils, 15 backs Yoke, 16 magnets, 17 circuit boards

Claims (5)

A centrifugal blower in which an impeller is housed inside a casing composed of an upper casing and a lower casing, and air is blown out of the casing from an opening formed on a side surface of the casing.
The impeller includes a disc-shaped shroud having an opening at the center, a disc-shaped main plate, and a plurality of blades provided between the shroud and the main plate.
When the diameter of the virtual circle passing through the inner peripheral edge of the blade is d and the diameter of the outer peripheral edge of the shroud is D,
The ratio d / D of the diameter d to the diameter D is smaller than the value at which the natural frequency of the impeller with respect to the ratio d / D is the lowest.
Centrifugal blower. The ratio d / D is approximately 0.2 or less.
The centrifugal blower according to claim 1. The ratio d / D is approximately 0.1 or more.
The centrifugal blower according to claim 2. The shroud, the main plate, and the blades are integrally formed.
The centrifugal blower according to any one of claims 1 to 3. The back yoke and magnet of the outer rotor type motor are fixed to the inner surface of the cylindrical wall provided on the surface of the main plate opposite to the shroud.
The centrifugal blower according to any one of claims 1 to 4.

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